Americans mostly use stove-top kettles. The kettle is filled with
water and then heated on a gas or electric stove. The water
boils, producing steam, which then flows out of the kettle spout
producing a whistle. The whistle signals that your water is ready
and you should turn off the stove.

Here's that process in action:

Vladeep/Shutterstock

I'm American, so when I moved to the UK, I was surprised that it
was difficult to find the standard stove-top kettle that I had
grown up with. They are almost all electric.

Most homes in the US operate on 100-127 volts, whereas the UK and
many other countries use between 220 and 240 volts. The lower
voltage in the US means that electric kettles would not heat
water as quickly as they do in the UK. As a result, they haven't
caught on in the US.

Mr. Reid gives this example:

To raise the temperature of one litre of water from 15°C to
boiling at 100°C requires a little bit over 355 kilojoules of
energy. An “average” kettle in the UK runs at about 2800 W and in
the US at about 1500 W; if we assume that both kettles are 100%
efficient† than a UK kettle supplying 2800 joules per second will
take 127 seconds to boil and a US kettle supplying 1500 J/s will
take 237 seconds, more than a minute and a half longer.

He concludes: "This is such a problem that many households in the
US still use an old-fashioned stove-top kettle."

One British person living in the US cited the voltage explanation
but also wrote that "the culture for it isn't there," perhaps
meaning that Americans drink less tea and aren't as fussed about
how fast water gets boiled.